Crustal movement and deformation in Taiwan and its coastal area

Based on the station velocity data obtained from Fujian coastal GPS network and Taiwan-Luzon GPS network and the data obtained from IGS permanent stations commonly used in the data processing of both networks, the uniformity of reference frames and velocity fields of both GPS networks is realized. It has been discovered from the analysis on the velocity field in Taiwan and its coastal areas that the horizontal crustal movements in the coastal area of Fujian, Taiwan Strait and the northern part of Taiwan Island are fully consistent. The movement direction is around 26.0E by S and the rate is about 39 mm/a. The opposite variation occurs in the coastal mountain area in the eastern part of Taiwan Island with the movement direction of 30.0N by W and the movement rate of about 33.3 mm/a. In the southern end of Taiwan Island, the movement direction is 50.0S by W and the movement rate is about 13 mm/a. If the geometric center of Fujian coast is used as the reference datum, Taiwan Island has a consistent (except its north end) NW-trending movement with the direction of around 50.0N by W. The maximum rate of 61 mm/a occurs along the eastern coast and decreases gradually towards west. The analysis of strain field indicates that Taiwan and its coastal area have a uniform strain field with the principal compressive strain direction of N48.0W and the principal tensile strain direction of N42.0E. The principal compressive strain rate along the eastern coast of Taiwan Island is 3.43610-7/a, which decreases gradually towards west and reaches 1.86110-8/a to Fujian coast. The collision and underthrust of Philippine Sea plate with Eurasian plate in the eastern part of Taiwan Island can be considered as the principal force for the crustal movement, deformation and great earthquake occurred in Taiwan and its coastal area. The direction of principal compressive stress in the area is about N55.0W.